Class 800LB Forged Stainless Steel Swing Check Valve (A182 F316) — 3/4", Reduced Bore, SW/NPT Ends

This Class 800LB forged stainless steel swing check valve is the 3/4" reduced bore design to BS 5352, with a bolted bonnet, swing disc and metallic seating surfaces. The body is forged ASTM A182 F316 stainless steel, with F316L available for improved intergranular corrosion resistance after welding. Socket weld ends are to ASME B16.11 and NPT threaded ends to ASME B1.20.1. The valve is API 598 tested and is specified for small-bore stainless process, instrument, utility and corrosive service lines.

Application

This 3/4" Class 800 forged stainless check valve is specified on small-bore stainless process lines in chemical and petrochemical plants, pharmaceutical and food-grade piping, offshore and marine utility systems, and instrument air and water lines where carbon steel would corrode. The forged F316 body gives corrosion resistance in oxidizing and mildly reducing media, the reduced bore gives a positive disc lift and fast closure at low flow, and the SW or NPT ends suit small-bore pipe schedules. For chloride-rich or sour service, F51 duplex body and NACE MR0175 compliance are available on request.

Standards

Design and manufacture: Forged steel check valve according to BS 5352.
Pressure-temperature ratings: ASME B16.34.
Socket weld end dimension: ASME B16.11.
Screw thread dimension: ASME B1.20.1 (NPT).
Butt-weld end (on request): ASME B16.25.
Flanged end (on request): ASME B16.5.
Material: ASTM A182 F316 / F316L; F51 duplex on request.
Inspection and test: API 598.
Sour service: NACE MR0175 / ISO 15156 on request.

Quick Details

1. Type: Forged stainless steel swing check valve
2. Design: Bolted bonnet, swing disc, reduced bore
3. Size: 3/4" (DN20); 1/2"–2 1/2" series available
4. Pressure Rating: ASME Class 800LB
5. End Connections: Socket weld (ASME B16.11), NPT threaded (ASME B1.20.1)
6. Body Material: ASTM A182 F316 (F316L optional)
7. Various trim materials available to suit service conditions; F51 duplex on request
8. NACE MR0175 on request
9. Test and inspection: API 598

Selection Notes: Forged vs Cast, RB vs FB, and SW vs NPT

Forged vs cast at Class 800: small-bore check valves in Class 800 are normally forged because the wall thickness and body shape at 3/4 inch are difficult to cast soundly, and forging gives a denser, more homogeneous section for high-pressure small-bore service. BS 5352 is the design standard for forged steel check valves, while BS 1868 covers cast steel check valves. The forged body also machines more predictably for the SW and NPT end preparations.

Reduced bore vs full bore: reduced bore (RB) has a flow port smaller than the nominal pipe bore, which increases flow velocity through the seat and gives a more positive disc lift and faster closing, at the cost of a higher pressure drop. Full bore (FB) matches the pipe bore and gives the lowest pressure drop but a slower, less positive disc action at low flow. This page is the RB version in 3/4 inch; FB is available on request. RB is normally specified where a compact body and positive closure matter more than pressure drop.

SW vs NPT ends: socket weld ends to ASME B16.11 give a permanent, leak-tight joint and are preferred for high-pressure, high-temperature, sour or toxic service where a threaded joint could loosen or leak. NPT threaded ends to ASME B1.20.1 allow faster assembly and disassembly and are common on utility, instrument and small-bore process lines. For NACE MR0175 sour service, SW ends are more frequently specified because the threaded joint is an additional leak path.

Features

1. General
Bolted bonnet;
Swing disc;
Reduced bore (full bore on request);
Metallic seating surfaces.

2. Pressure-Temperature Ratings
Ratings to ASME B16.34; Class 800 at 100°F (38°C) is 1975 psi (13.8 MPa) for ASTM A182 F316. Refer to ASME B16.34 for the derating curve at elevated temperature.

3. Body and Bonnet Connection
Class 800LB forged check valves are supplied with a bolted bonnet as standard; welded bonnet and pressure seal bonnet are available on request.

4. Cover Gasket Style
Stainless steel + flexible graphite wound gasket is used for Class 800LB stainless check valve;
Metal gasket and metal ring gasket are also optional.

5. Seat
For stainless steel check valve, an integral seat is usually adopted, or it can be machined integrally after hard alloy welding. The seat sealing surface may be spray-welded with hard alloy if specified by the customer.

6. Bore Type
Full bore (FB) and reduced bore (RB); this page is the RB version.

Forged Stainless Steel Swing Check Valve Parts and Material List (Class 800LB)

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Parts numbers follow the original drawing; numbers not listed are lift-type or ball-type parts and do not apply to this swing-type valve. Part 33 "Steel ball" in the original source is a ball check valve part and has been removed. Gasket corrected from "316+ Flexible garphite" to "316 + Flexible graphite". Disc Nut corrected from "8M" to "B8M". Confirm B8 vs B8M bolting against the material certificate; B8M is standard for F316 bodies.

Main Connection Dimensions — Class 800LB Reduced Port Swing Type (mm)

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Dimensions in mm. L = face-to-face dimension for SW / NPT ends. H = centreline to top of bonnet. d = flow port diameter (reduced bore). The original source table mixed lift-type and full-port (FP) data in the same rows; this table has been filtered to the reduced-port (RP) swing-type series only, matching the RB swing product on this page. In the original data the flow-port values "105" and "135" and the weight values "14" and "15" had lost their decimal points; they are corrected here to 10.5, 13.5, 1.4 and 1.5 respectively. Full-bore (FB) and lift-type dimensions are available on request.

Frequently Asked Questions